Internet users have unleashed unusually high levels of vitriol towards the government in the wake of the crash, and even state newspapers have severely criticised the way authorities handled Saturday's collision in eastern China.

Bill Bishop, a Beijing-based independent analyst, said the "remarkably uncensored" coverage was a marker of the intensity of public feeling about official corruption in China.

"It's quite amazing to see what is going on, because there's a lot of venom and animosity directed towards the government," he said.

"People with huge amounts of followers (on Sina's popular Twitter-like Weibo service) have been extremely aggressive because they're sick of the corruption and the dynamic that allows this kind of mess to happen with the railways."

Already before the crash, which left at least 39 people dead and nearly 200 others injured, criticism of rail authorities online and in the press was rife, following problems with a Beijing to Shanghai high-speed line and graft cases.

In February, Beijing sacked then railways minister Liu Zhijun for allegedly taking more than 800 million yuan ($124 million) in kickbacks, and auditors later uncovered corruption linked to the Beijing-Shanghai project.

The public anger found its focus when a high-speed train careered into a second train on Saturday on the outskirts of Wenzhou city, in an apparent failure of the Chinese-made signalling system.

In the past few days, bloggers have questioned whether the true death toll might be higher than that officially released, and whether the high-speed rail system is being developed too fast.

Premier Wen Jiabao on Thursday travelled to Wenzhou to visit the scene of the crash -- a move Internet commentators interpreted as a victory.

"The central government would never in a million years have thought Weibo could bring so much trouble," one posted on Sina's Weibo.

But Qiao Mu, professor of international political communications at the Beijing Foreign Studies University, said the government would not tolerate such challenges indefinitely.

"I'm worried that after this accident is over, officials will tighten control over Weibo, because Weibo challenged rulers' authority," he said.

China's state-controlled media has also been unusually outspoken in its coverage of the accident, defying directives not to question the official line.

A comment piece on the front page of the People's Daily, the Communist party mouthpiece, said Thursday that China "needs development, but does not need blood-smeared GDP".

"Development is of overriding importance. But development should not be pursued at all cost," said the article, which was attributed to "the newspaper's commentator".

That followed an editorial in both the English and Chinese versions of the state-run Global Times that contrasted the "bureaucratic" attitude of officials with a booming "public democracy" online.

Zheng Yongnian, an Internet and politics expert at the National University of Singapore, suggested the extraordinary latitude given to media and online users could be the result of a power play ahead of a leadership change next year.

He said the railway system was consolidated under the leadership of the former president Jiang Zemin, and despite major problems along the way -- such as a deadly train crash in 2008 -- little had been done to reform it.

"There's been major vested interests in the railway system. It's very difficult to deal with... But now with such a major crisis, it's a good opportunity to deal with the issue," he said.

David Bandurski of the University of Hong Kong's China Media Project said mainland press had grabbed this opportunity "aggressively".

"The (Communist) party right now has completely lost the agenda on this story. If you look, you can see signs of how they are asserting control, but so far it's been largely ineffective," he said.

Bandurski, however, warned it would be "foolish" to think this marked a new beginning for China's media and Internet.

He compared the current situation to the 2003 outbreak of the deadly SARS epidemic, which saw authorities giving latitude to the press before gradually reasserting control, handing out penalties to 10 different media.

"They waited in the wings until the crowds dispersed -- metaphorically -- and then they went after them individually. That's pretty typical," he said.